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59. R Krahe, K.R. Kinsman, and H. I. Aaronson: Acta Metall., 1972, vol. 20, p. 1109. 60. T.Y. Hsu, G. Wengui, and Y. Xuejie: Proceedings of an International Conference on Solid-Solid Phase Transformations, TMS-AIME, Warrendale, PA, 1983, p. 1029. 61. T.Y. Hsu: The Formation and Application of Low-Carbon Martensitic Structure, Association of Heat Treatment, Shanghai, RR.C. 62. H.I. Aaronson: unpublished research, Carnegie Institute of Technology, Pittsburgh, PA, 1954. 63. C. Laird and H.I. Aaronson: Acta Metall., 1969, vol. 17, p. 505. 64. R. Sankaran and C. Laird: Acta Metall., 1974, vol. 22, p. 957. 65. K.R. Kinsman and H. I. Aaronson: Discussion to Ref. 51, p. 33. 66. K.C. Russell, D.M. Barnett, C.J. Altstetter, H.I. Aaronson, and J. K. Lee: Scripta Met., 1977, vol. 11, p. 485.
Authors' Reply H. K. D. H. BHADESHIA and D. V. EDMONDS
In this note we demonstrate that the discussion ~ of "The Bainite Transformation in a Silicon Steel", 2 as submitted by Liu et al., is not correct. We restrict our discussion to the scientific content of Reference 1. The Incomplete Reaction Phenomenon. It has been demonstrated that in controlled experiments, the formation of bainitic ferrite during isothermal transformation ceases well before the carbon concentration of the residual austenite reaches the level given by the extrapolated paraequilibrium Ae3' (a + y ) / y phase boundary. 3'4'5 This effect is called the "incomplete reaction phenomenon" and eludicates the mechanism of the bainite transformation in steels, as discussed elsewhere. 3-6 Here we focus on the claim ~ that the incomplete reaction phenomenon is not general. The much-quoted I and unpublished evidence of Boswell et al. 7 is difficult to accept; the role of carbide precipitation in the Fe-Mo-C alloys used does not seem to have been taken into account, and it has not been established that the transformation products examined exhibit an invariantplane strain surface relief effect which has an appreciable shear component. Indeed, the metallographic and other essential experimental details remain unpublished. The experiments 1 on the Fe-3.11Mn-0.38C and Fe1.73Si-0.38C (wt pct) alloys would appear to be inadequately designed, as far as the testing of the incomplete reaction phenomenon is concerned. With the heat-treatment method used, the Fe-Si-C alloy simply does not have the hardenability necessary to ensure that transformation occurs only at the isothermal transformation temperature of interest. This is emphasized by the experiments 8 in which the same alloy (and experimental technique) was reported to lead to ferrite formation at a temperature where thermodynamic data indicate the presence of only austenite, the implication being that the ferrite actually formed during the quench from the isothermal transformation temperature. This would also explain the apparently faster growth rate s of allotriomorphic ferrite in this alloy, compared with that predicted by carbon diffusion controlled growth occurring under paraequilibrium conditions. In fact, the use ~'s of specime
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